Schizophrenia may occur, in part, because brain development goes awry during adolescence and young adulthood, when the brain is eliminating some connections between cells as a normal part of maturation, results of a study suggest. The new report appears online July 8, 2008 in Molecular Psychiatry.

Comparing a group of adolescents and young adults who had recently had their first bout of schizophrenia with a group of healthy peers, researchers found that this loss of tissue began around the same time and in the same brain areas in both groups. But the rate of loss was more pronounced and covered a greater area of the brain's surface in the youth with schizophrenia.

The new finding adds to evidence that changes in brain development which lead to schizophrenia aren't limited to the prenatal stage and early childhood, but also occur during the late-teen and young-adult years - the ages when symptoms usually begin to appear.

To conduct their studies, the researchers performed magnetic resonance imaging (MRI) in 16 adolescents and young adults, ages 17 to 30, with recent-onset schizophrenia and in 14 healthy people in the same age range. The MRI studies were repeated two years later, to look for changes. Advanced techniques helped ensure the validity of the results.

The scans showed the expected loss of brain volume in both the healthy group and the group with schizophrenia, an indication that the normal tissue loss was taking place. Compared with healthy youth, however, those with schizophrenia had more tissue loss on the surface of one of the last areas of the brain to develop - the prefrontal lobe, which controls higher functions like thinking, judgment, and memory. These functions are impaired in people with schizophrenia.

The timing of the excessive tissue loss in this late-developing brain area corresponds with the age that schizophrenia symptoms usually begin, the researchers note.

The youth with schizophrenia also had more evidence of tissue loss on the surface of the brain's parietal lobes, which help process sensory information coming in from the outside world, such as visual or tactile information. Abnormal sensory perceptions are common in people with schizophrenia, who often see and hear things that aren't there, or misinterpret what they see and hear to mean something else.

In both the prefrontal and parietal lobes, the excess pruning progressed over the two years in the group with schizophrenia. Overall, the group with schizophrenia group had 1.6 times more evidence of tissue loss in the surfaces of these lobes, compared with the healthy group.

Other studies of schizophrenia have implicated variations in certain genes in the disease. The authors of the new study note that these genes are known to affect the connections between brain cells.

The study was a collaboration between investigators at the University of Melbourne, headed by Christos Pantelis, MD, and Patrick McGorry, PhD, and investigators at the University of California, Los Angeles, headed by Tyrone Cannon, PhD, Arthur Toga, PhD, and Paul Thompson, PhD.